MADISON, Wis.—During what police say was a 20-year killing spree in Milwaukee, Walter Ellis left his DNA behind all along the way—everywhere but the one place where it might have saved a life.

Ellis should have given a DNA sample to the state crime databank during a prison stint in the early part of this decade, but he had another inmate pose as him, authorities say. As a result, when analysts tried to identify DNA in bodily fluids from one of the slayings back in 2003, no matches turned up.

Investigators didn’t connect Ellis to the crimes until this fall, when they seized genetic material from his toothbrush. By then, it was too late for the woman police say was Ellis’ seventh and final victim.

“If they would have got his DNA when they were supposed to get it, maybe my cousin would still be here,” said Sarah Stokes, whose cousin, 28-year-old prostitute Ouithreaun Stokes, was found beaten and strangled in an abandoned rooming house in 2007.

An Associated Press review found tens of thousands of DNA samples are missing from state databanks across the country because they were never taken or were lost. The missing evidence—combined with big backlogs at the nation’s crime labs that result in DNA samples sitting on shelves for years without being analyzed and entered into the databanks—is preventing investigators from cracking untold numbers of cases. And some of those gaps have had tragic consequences.

“If you got missing samples, some of those people are out there raping your wives and abducting and murdering your children this week,” said former Charlottesville, Va., police Capt. J.E. Harding, who helped uncover missing samples in that state during a search for a serial rapist.

Crime lab supervisors, state police and prison officials blame the failure to collect samples on new and confusing laws and a lack of coordination among the many different law enforcement agencies and institutions responsible for taking DNA.

“I would just about guarantee you every state has an issue with this,” said Lisa Hurst, who tracks DNA convictions for Gordon Thomas Honeywell, an organization that lobbies on public safety and biotechnology issues.

The AP review found 27 states either failed to collect some DNA samples or are unable to say whether they took one from every offender who owes one.

The case against Ellis, who is set to go trial this spring, prompted an audit in Wisconsin that found 12,000 convict samples are missing. The AP review further found that Illinois failed to get DNA from about 50,000 offenders, Colorado from 2,000, and Virginia from about 8,400.

Exactly how many samples are missing across the country is unknown. The National Institute of Justice estimated in 2003 that offenders owed up to 1 million uncollected samples and as many as 300,000 samples may be waiting for processing. The backlog grew to about 450,000 by 2008. The institute had no updated estimate of uncollected samples.

At least 13 states are dealing with more samples than they can handle. Kansas, for example, has nearly 40,000 on its crime lab shelves, waiting for upload.

Police in Columbus, Ohio, say Robert N. Patton Jr. committed 37 rapes over a decade and a half. As with Ellis in Milwaukee, he could have been stopped earlier.

Patton had submitted his DNA in 2001 while behind bars for burglary, but it was not entered into the database until 2004, two days before he climbed through an apartment window and raped Diana Cunningham. Police say he attacked 13 women in all after supplying his DNA.

If Patton’s genetic material “had been processed in a timely fashion, he never would have gotten to me or gotten to any of the others,” said Cunningham, now 25. “It’s scary how many more people are going to be victimized because their attackers aren’t going to be caught. And it would be so easy for them to be caught if they could make the matches.”

Patton is now serving a 68-year prison sentence.

State databanks contain hundreds of thousands of samples. The FBI’s national database, built with states’ uploads, held 7.4 million as of September.

Over the past 15 years, tough-on-crime legislators expanded laws to require DNA from more offenders. First it was sex offenders. Today, 47 states demand DNA from every convicted felon. Twenty-one take it from anyone arrested for homicide or a sex crime, according to Gordon Thomas Honeywell.

Generally, prison officials collect DNA from inmates as they enter the institution, often by swabbing the prisoner’s mouth. Local police, sheriff’s departments or probation officers are also supposed to take samples. That means a profusion of collection points.

But the laws are so fluid that the agencies responsible for collecting DNA struggle to track which offenders owe samples, authorities say. The New Mexico lab has taken to sending wall charts to sheriff’s departments to help them keep things straight.

Wisconsin Gov. Jim Doyle has blamed his state’s missing DNA, in part, on confusion over the laws during the early days and no clear idea of who was in charge.

Roughly half the states have some cross-check between their labs and prison systems to ensure everyone who owes a sample has given it, the AP found. For example, Michigan DNA administrators and state prison officials compare information annually. Virginia requires that it be done quarterly. But half the states have no such procedures.

Robyn Quinn, Delaware’s DNA database administrator, said she is sure her state is missing DNA, but has no idea how much, citing lack of communication between her office and the Corrections Department.

“The other end is a black hole for me. We have no way of getting into their system to see who is supposed to be collected,” she said. “I am waiting for something to hit the fan, if you will.”

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